Check valve

ABSTRACT

A flapper or wafer-type check valve with two half-disc flapper or wafer closure elements pivotally mounted in the valve body by hinges on a shaft extending transversely of the valve&#39;&#39;s flow passage, and shaft guides that removably but securely retain the shaft in the valve body while facilitating limited movement of the shaft parallel to the flow passage axis. The curved and straight peripheries of the flappers close against a seat on the valve body comprising an annular shoulder extending into the flow passage and a transverse rib that extends across the flow passage parallel to the shaft. When opening from a closed position, the flappers first lift off the seat in the area of the hinges before they begin to pivot about the shaft, and as the flappers close they come to rest against the hinge area of the seat without sliding or rubbing against it, thereby avoiding wear of the seat. In addition, several different systems for securing the shaft guides to the valve body are disclosed, as are valves with resilient seats mounted on the flappers, on the valve body, and also valves with non-resilient seats.

United States Patent Satterwhite et al.

[451 July 25, 1972 [54] CHECK VALVE [7 2] lnventors: Lawrence E.Satterwhite; Alton M. Wil- 22:12; Attorney-F. w. Anderson, c. E. Trippand w. w. Ritt,.lr. Houston, Tex.

[73] Assignee: FMC Corporation, San Jose, Calif. ABSTRACT [22] Filed:Sept. 16, 1970 A flapper or wafer-type check valve with two half-discflapper or wafer closure elements pivotally mounted in the valve body[2]] Appl 72361 by hinges on a shaft extending transversely of thevalves flow passage, and shaft guides that removably but securely retain521 US. Cl ..1s7 s12.1, 137/5 l 2.5, 137/5151 the shaft in the valveWhile facilitating/mil "mvemem [51] of the shaft parallel to the flowpassage axis. The curved and [58] Field of Search ..l37/5 l 2, $12!,512.5, 515.7, g t peripheries of the flappers close against a seat onthe 137/515, 4542, 527, 527.4, 516.29 valve body comprising an annularshoulder extending Into the flow passage and a transverse nb thatextends across the flow 56 R f Cited passage parallel to the shaft. Whenopening from a closed l e flames position, the flappers first lift offthe seat in the area of the v UNITED STATES PATENTS hinges before theybegin to pivot about the shaft, and as the flappers close they come torest against the hinge area of the 3,276,471 10/1966 Hagner ..l37/527seat without Sliding or bi against i thereby avoiding 3,378,030 4/1968 f"137/516 29 wear of the seat. In addition, several different systems for3,007,488 11/1961 7 "137/5121 x securing the shaft guides to the valvebody are disclosed, as 1/ 1963 F "137/5274 x are valves with resilientseats mounted on the flappers, on the 3,395,727 8/1968 welse 1 x valvebody, and also valves with non-resilient seats. 3,452,778 7/1969 Babcock....137/5l2.l

3,538,946 1 1/1970 l-lilsheimer ..l37/512.1 17 Claims, 15 DrawingFigures 34 s20, 54a 22 -h.\ t 2o e.

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Patented July 25, 1972 3 Sheets-Sheet 5 F'IE lEl 4. P \5 6 O H n6 4 P Mm6 4 n a F'IE 1 1 F'IE'| lE| CHECK VALVE BACKGROUND OF THE INVENTION Thefield of art to which the present invention pertains includes checkvalves with closure elements of the flapper or wafer variety, whereinthe flappers or wafers are pivotally mounted on a shaft for movementbetween open and closed positions in the valve's flow passage inresponse to change in direction of the fluid flowing through the valve.The invention also relates to check valves of the aforementioned typewherein the flappers are spring-biased towards their closed position,and to systems that facilitate opening and closing of the flapperswithout causing wear of the valve seat, be it resilient ornon-resilient.

The flapper or wafer-type check valve has found wide acceptance in manyindustries where automatic prevention of reverse fluid flow in a pipeline or other such conduit is required. However, unless the flappers aresomehow able to lift off, i.e., move perpendicularly away from, thesurface of the valve's seat before they begin to pivot about theirsupporting shaft into an open position, they slide or rub on the hingearea of the seat during the initial phase of their opening movement,thereby causing undesirable abrasion and wear of this vital seatelement. Since this same type of wear also occurs during closure of theflappers as they complete their pivotal movement about the shaft, thelife of the seat in a valve of this type is undesirably shortened,especially where the seat is constructed of resilient material and usedin very active service.

Numerous attempts have been made to overcome this problem, and patentshave been granted on several proposed solutions thereof, including US.Pats. Nos. 3,007,488, 3,026,901, 3,072,141, and 3,074,427, all issued toJoseph S. Wheeler, .lr. Seat wear allegedly is reduced in some valves ofthis type by extending the ends of the closure spring outward past thecentroid of the flappers, and elongating the holes in the flappershinges and the valve's body through which the supporting shaft passes.It has been found that such elongated holes are undesirable, primarilybecause the small contact area between the shaft and the holes tends toincrease the size of the holes during operation of the valve,utilimately requiring replacement of the flappers and on occasion, thevalve's body itself. Furthermore, mounting the shaft in holes extendingentirely through the wall of the body is undesirable, for leakage canoccur through these holes in the absence of adequate seals, therebyincreasing the cost of maintenance.

SUMMARY Faced with the foregoing problems, and as a result of efforts tosolve them, applicants have invented a new flapper-type check valve thatemploys a novel system for supporting and retaining the flappers in thevalve body. More particularly, this invention involves securing theshaft, upon which the flappers are pivotally mounted, to guides that areretained in elongated grooves that extend in an axial direction in thebore or flow passage of the valve body. The guides are able to move inthese grooves a limited distance in the direction of the flow passage'saxis, so that the flappers lift off of the valve seat in the area of thehinges before they begin to pivot, thereby avoiding all sliding,rubbing, or other abrasive wear of the seat. Likewise, as the flappersclose they complete their pivotal movement about the supporting shaftbefore they contact the seat in the hinge area, thereby also avoidingwear of the seat during closure. In end result, this inventioneffectively precludes all problems with respect to wear of the seatduring either opening or closing of the valve, hence greatly prolongingthe life of the seat.

The invention further includes several different arrangements forsecuring the shaft guides to the valve body, each arrangement forfacilitating easy and quick installation and removal of the shaft andthe flappers for efficient assembly and disassembly of the valve. Theinvention is functional in valves with resilient or non-resilient seats,and wherein the resilient seats are affixed to the flappers or to thevalve body itself.

Accordingly, one object of the present invention is of provide a newflapper or wafer-type check valve, and especially to provide such avalve with a new system for mounting the flappers in the valve body.

Another object of the present invention is to provide a new means forretaining a check valves flapper hinge shaft in the valve body so thatthe flappers will lift off from their seats as the valve opens, andcorrespondingly will close against these seats as the valve closes,without rubbing or sliding on the seats, thereby eliminating a majorcause of wear of the seats.

Still another object of the present invention is to provide a new typeof mechanism for retaining the valve closure elements in a check valvebody such that they can be quickly and easily installed and removed forservice or replacement.

Yet another object of the present invention is to provide a new guidesystem for securely yet removably retaining the hinge shaft in aflapper-type check valve body, while simultaneously facilitating theshafts radial displacement in the direction of the valves flow passageaxis to allow the flappers to seat and unseat without sliding orotherwise moving with respect to the seat in a manner to cause unduewear thereof.

These and additional objects of the invention will become apparent uponreference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in elevation of thedownstream end of a valve according to this invention, with a portionbroken away to better illustrate the outside configuration of the valve's body.

FIG. 2 is a view taken on line 2-2 of FIG. 1, and on a reduced scale,showing the valve as it appears when fully closed and installed betweentwo pipe flanges.

FIG. 3 is a view like FIG. 2, showing the valves flappers unseated inthe area of the hinges just prior to pivoting into open position.

FIG. 4 is a view like FIG. 3, showing the valve as it appears when fullyopened.

FIG. 5 is a fragmentary section taken along line 5-5 of FIG. 1, showingthe relative positions of the valve body, flapper, shaft, shaft guide,and retaining screw, when the valve is fully closed.

FIG. 6 is a view like FIG. 5, showing another arrangement that employs aresilient pin for securing the shaft guide to the valve body.

FIG. 7 is a view like FIGS. 5 and 6, showing a split ring arrangementfor securing the shaft guide to the valve body.

FIG. 8 is a view like FIGS. 5-7, showing a threaded cap screw employedto secure the shaft guide to the valve body.

FIG. 9 is a view like FIGS. 5-8, showing a spring-biased lock pin forsecuring the shaft guide to the valve body.

FIG. 10 is a view like FIGS. 5-9, showing a threaded pipe plug with anelongated nose for securing the shaft guide to the valve body.

FIG. 11 is another view like FIG. 10, showing a modified version of thethreaded pipe plug arrangement of FIG. 10.

FIG. 12 is a view like FIGS. 5-11, but including the pipe flanges ofFIG. 2, showing how the shaft guide may be retained in the valve body bya pipe flange of appropriate size.

FIG. 13 is a view similar to FIG. 4, showing a valve like that of FIG. Ibut with the resilient seat positioned in and attached to relieved areasof the valve body.

FIG. 14 is a view of the valve of FIG. 13, but in a fully closedcondition.

FIG. 15 is a view like FIG. 14 showing another version of a valveaccording to the invention, this version having no resilient seat.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As illustrated in the drawings,a valve assembly 20 according to this invention comprises a valve body22 of annular configuration with a bore 24 and sealing surfaces 26, 28(FIG. 2) on its upstream and downstream ends, respectively, which aretightly secured against opposing pipe flanges 30, 32 by bolts 34 whenthe valve is installed in a pipeline. Usually a fluid seal, such as anannular gasket 36, is provided between the valve body 22 and the pipeflanges 30, 32, so that the bore 24 of the valve essentially becomes anintegral part of the pipeline.

The bore 24 functionally provides a cylindrical flow passage 38 throughthe valve body 22. An annular flange 40, with a downstream-facingsurface 42, extends radially into the flow passage, and a transversepost 44, with a downstream-facing surface 46, extends diametricallyacross the flow passage. The surface 46 intersects,-and is coplanarwith, the surface 42, and in this version of the valve these twosurfaces together support a valve seat 48 of rubber or other suitablematerial.

Two generally flat valve closure elements or flappers 52, 54, eachshaped generally like one-half of a disc, are pivotally mounted by theirhinges 56, 58, respectively, on a supporting shaft 60 that extendsacross the flow passage 38 parallel to the post 44. The shaft 60 iscarried or secured in the valve body 22 by shaft guides 62, 64 thatreside in longitudinal slots 66, 68, respectively, in the surface of thevalve bore 24. The flappers 52, 54 preferably are identical, having flatand smooth downstream surfaces 52a, 54a that come to a fluid-tight restagainst the valve-seat 48 when the valve closes (FIG. 2), thuscompletely shutting off flow through the valve.

When the flappers are in their fully opened position as illustrated inFIG. 4, they rest against the sides of the guides 62, 64, which in thisversion are relieved to form central longitudinal stop ribs 620, 64a. Itshould be noted, however, that the sides of the guides need not berelieved to form these stop ribs, and instead can extend uninterruptedbetween the guides top and bottom surfaces, such as if the guide isconstructed from rectangular barstock.

The holes in the hinges 56, 58 preferably are large enough to facilitatefree pivoting of the flappers on the shaft 60, but are not elongated inany direction. If desired, suitable washers 70 can be included betweenthe hinges 56, 58, and also between the hinges and the shaft guides 62,64, to insure freedom of movement between these elements.

A helical spring 72, surrounding the central portion of the shaft 60between the hinges 56, 58, has ends 72a, 7212' that bear againsttheflappers 52, 54, respectively, to bias them into their closedposition as illustrated best in FIG. 2. The force exerted by the helicalspring against the flappers is suflicient to hold them generally in theclosed position, and to facilitate their automatic closure when fluidflow through the valve in the direction of the arrows in FIG. 3 ceases,thereby preventing undesired reversed flow through the valve in thedirection of the arrows in FIG. 2.

The shaft guides 62, 64 (FIGS. 1-5) are identical, so that the followingdescription of guide 64 pertains equally to guide 62. As seen best inFIG. 5, the guide 64 has a vertical bore 74 for receiving and retainingthe shaft 60, and a horizontal longitudinal bore 76 through which aretainer screw 78 extends. The bore 76 is counterbored at 760 toaccommodate the screws head 78a, which is of larger diameter than thebore 76. Therefore, when the screw is threaded into the tapped hole 80in the valve body 22, it securely retains the shaft guide 64 in the slot68.

When the valve is fully closed, the head 78a of the retainer screw 78 isspaced from a shoulder 64b (FIG. at the bottom of the guides counterbore76a. This spacing permits the guide 64, and hence the shaft 60 and theflappers 52, 54, to move downstream as the valve begins to open, untilthe shoulder 64b contacts the screw head 78a. As this movement occurs,the flappers lift off the valve seat 48 in the area of their hinges 56,58, sufficiently to enable their straight edges 52b, 54b to clear theseat 48 as they pivot on the shaft 60 towards their open position.However, because of the restriction imparted by the screw head 78aagainst further longitudinal movement of the shaft guide 64 with respectto the valve body 22, the guide, the shaft, and the flappers arepositively retained as an assembly in the valve body, yet can easily andquickly be removed therefrom by unthreading the screw 78 from the tappedhole 80.

The foregoing system also functions to prevent wear of the seat 48 whenthe valve closes, for the'flappers complete their pivotal movement aboutthe shaft 60 before they finally move into sealing contact with the seat48 in the area of their hinges. In other words, during closing theflappers arrive first at the position shown in FIG. 3, and then moveinto the FIG. 2 position to establish a fluid-tight seal with the seats48. Therefore, all wear of the seats 48 from sliding, rubbing, etc.contact by the flappers 52,54 is effectively precluded by thisinvention, resulting in significantly greater longevity of the seat.

This elimination of wear of the seat 48 is also achieved when it issecured to the flappers 52, 54 instead of to the surfaces 42, 46 of thevalves body 22. In this arrangement, which would of course involve aseparate seat on each flapper, as the valve opens the seats lift off thesurface 46-of the post 44 before the flappers being to pivot towardstheir open position about the shaft 60, so that as this pivotal movementoccurs the seats clear the edges of the posts surface 46. Likewise, asthe flappers close they complete their pivotal movement in a closingdirection about the shaft 60 before the seats contact the post's surface46 or its edges. Hence, no abrading or sliding movement between theseats andthe post area of the valves body occurs, and wear of the seatsfrom such causes is precluded.

As seen in FIG. 5, when the flappers are fully closed against theresilient seat 48, the forward end 64c of the shaft guide 64 is spacedfrom the surface 46 of the transverse post 44. This spacing facilitatesfurther longitudinal movement of the guide 64 upstream to enable theflappers 52, 54 to compress the seat 48 sufficiently to establish afluid-tight seal with it. Because of the fact that seats of variousthicknesses and resiliencies may be employed in valves of this type,this space is proportionately dimensioned to accommodate any upstreammovement necessary to establish a compressive seal with the particularseating element involved.

FIG. 6 illustrates a modified version of the valve assembly 20, with ashaft guide 90 retained in the valve body 22 by means of a pin 92 thatslidably fits into a hole 94 in the guide 90 and extends into an opposedlongitudinal closed-end slot 96 in the body 22. The pin 92 can be acomposite of a rubber or other resilient upper portion 92a, and a nylonor other relatively rigid lower portion 92b. The resilient portion 92ais sufficiently compressibleto facilitate pushing the rigid portion 92entirely into the shaft guide hole 94 so that the guide can be installedin the valve body 22. When the pin 92 arrives opposite the slot 96, therigid portion 92b will be forced by the resilient portion 92a into theslot, locking the shaft guide 90 into the body 22. Note that in thislocked position the rigid portion 92b of the pin 92 resides also in theguide's hole 94, thus achieving a durable retention of the guide 90 inthe valve body 22. As shown in FIG. 6, the length of the slot 96 issufiicient to facilitate adequate longitudinal movement of the guide 90so that the flappers clear the valve seat 48 when they pivot on theshaft 60. As a variation, if desired, the pin 92 can be entirelyresilient so long as it has the required capability for retaining theguide 90 in the slot; for example, a sufficiently strong spring coulditself be used for this purpose.

Another modified version of the valve assembly 20 is shown in FIG. 7,wherein the shaft guide 100 has a transverse slot 102 that, wheninstalled in the valve body 22, is opposite to an internal annulargroove 104 in the body 22. A split ring 106 of steel or other suitablerigid material fits into the slot 102 and the groove 104 to lock theguide into the valve body 22. The ring 106 is sufficiently constrictableto facilitate insertion of the shaft guide 100 into the valve body 22until the slot 102 is positioned opposite the groove 104, at which timethe split ring self-expands into the groove 104. Tl'le width of thegroove 104 is dimensioned to facilitate longitudinal movement of theguide necessary to insure clearance of the valve end slot 116, in thevalve body 22. The capscrew 112 is proportioned lengthwise to engage theslot 116 when it is threaded completely into the shaft guide 110, sothat by partially unthreading the screw 112 the guide can be inserted orremoved from the valve body. As with the slot 96 in the version of FIG.6, the slot 116 is of sufficient length of facilitate movement of theguide 110 longitudinally a distance adequate to let the flappers pivoton the shaft 60 without touching the valve seat 48.-

In FIG. 9 the shaft guide 120 is retained within the valve body 22 by apin 122 that extends from a hole 124 in the guide into a longitudinalclosed-end slot 126 in the valve body 22. The pin 122 is biased by acoil spring 128 towards the slot 126, and thus is held in that slot whenthe guide is installed. A smaller diameter portion 122a of the pin 122extends through a commensurately sized hole 130 in the guide 120 tofacilitate withdrawal of the pin 122 from the slot 126, so that theguide can be easily removed from the valve body 22. As in the versionsof FIGS. 6-8, the slot 126 is long enough to permit longitudinalmovement of the guide 120 sufificient to insure the flappers will clearthe valve seat 48 as they pivot on the shaft 60 In the version of thevalve assembly illustrated in FIG. 10, the shaft guide 132 is retainedwithin the valve body 22 by a pipe plug 134 threaded into a tapped hole136 in the guide. The pipe plug has an elongated nose section 138 thatextends through a bore 140 in the shaft guide 132 and into alongitudinal closed-end slot 142 in the valve body 22. Thus, bythreading the pipe plug 134 into or out of the shaft guide 132, theguide can be easily locked into the valve body 22 or removed therefrom.The nose section 138 can be integral with the pipe plug 134, or it canbe a separate element, such as a dowel, a roll pin, or a spring pin thatis pressed or threaded into the plug. Here again, the length of the slot142 affords movement of the guide away from the post 44 to assureclearance of the valve seat 48 by the flappers as they pivot on theshaft 60.

FIG. 11 illustrates a modified version of the structure of FIG. 10,showing a pipe plug nose section 150 with an enlarged head 152. The nosesection 150 is fixed to the pipe plug 134, and the shaft guide 154 isrelieved at 156 to receive the head 152 when the pipe plug isunthreaded, so that the shaft guide can be readily inserted or removedfrom the valve body 22. The head 152 also serves as a safety measure inthat if the pipe plug 134 should accidentally become unthreaded when thevalve is in use, the head will prevent it from being carried away byfluid flowing through the valve. As with the previously describedversions, the head 152 extends into an elongated longitudinal slot 158that is long enough to facilitate movement of the guide 154 downstream asuflicient distance to let the flappers clear the valve seat 48 as theypivot about the shaft 60.

FIG. 12 illustrates the valve assembly 20 mounted between two opposedpipe flanges 160, 162 with an inside diameter equal to the diameter ofthe valve bore 24. Since the pipe flange 162 effectively constitutes anend to the slot 68 in the valve body 22, it thereby prevents furtherlongitudinal movement of the guide 164 away from the post 44, thusconfining the guide within the slot. Accordingly, where the valve boreand the inside diameter of the pipe flange on the downstream end areequal, there is no need for any additional retaining elements such asthe previously described cap screws, pins, pipe plugs, etc., to insurethat the guide will remain in place. Here, the space between thedownstream end 164a of the guide, and the face of the pipe flange 162 orthe gasket 166 if one be employed, must be sufficient to facilitatelongitudinal movement of the guide for the required flapper clearancefactor previously explained.

Therefore, as is apparent from the foregoing description of the severalversions of this invention, regardless of which retaining system isused, the guides are free to move longitudinally in the slots a limiteddistance to let the flappers lift off of the seat 48 in the area of thehinges, as shown in FIG. 3, be-

position into the position shown in FIG. 3, and subsequently into thefully closed position of FIG. 2.

It should also be observed that when the valve assembly 20 I isinstalled against a downstream pipeline flange having an end face thatoverlaps the downstream or open ends of the slots 66, 68, these slotsare thereby effectively closed, thereby precluding further longitudinalmovement of the shaft guides in the slots. Such a relationship providesa secondary retaining system for assuring that the guides, the shaft andthe flappers will not move out of operative position in the valve body.

As is illustrated in FIGS. 13 and 14, the invention also can be embodiedin a valve wherein the resilient seat is positioned in a relieved orgrooved area in the valves body. In this version the surface 42 of thevalves body 22 is provided with an annular groove 170, and the surface46 of the post 44 is grooved at 172. The groove 172 intersects thegroove 170 at diametrically opposite points to form a continuousrelieved area in which a pair of resilient seats 174, 176 are secured,each seat completely encircling one of the upstream flow passages P.Both seats are axially dimensioned to extend out of the grooves 170, 172past the downstream-facing surfaces 42, 46, and each seat has atransverse dimension less than the width of the grooves so that a voidexists between the grooves and the seats when the valve is open (FIG.13). When the valve is closed (FIG. 14) and under pressure in thedirection of the arrows, the flappers 52, 54 rest against the surfaces42, 46, thereby compressing the seats in the amount of their extensionout of the grooves 170, 172. The void space in the grooves allows theseats to yield to this compressive force without exceeding their elasticlimits, so that they will return to their original configuration, asshown in FIG. 13, when the flappers open in response to a pressurebuildup in the direction opposite to the arrows of FIG. 14. When thevalve is closed, the void in the grooves not occupied by the displacedseat material will allow the pressure to force the seat material towardthe contact area of the flappers and the surfaces 42, 46 between thegrooves and the upstream flow passages P, thereby energizing orenhancing the seal.

As has been mentioned earlier, this invention also can be employed witha valve having no resilient seat, i.e., a valve in which the flappersclose directly against the surfaces 42, 46 of the body 22, as shown inFIG. 15. The flappers will open and close in the same manner andmovement as when a resilient seat is present, and thus wear of theflappers surfaces in their hinge area from rubbing or sliding on theadjacent valve body surfaces and edges of the post 44 is avoided. Thisis an important feature particularly in valves having relatively softmetal flappers, and that are subject to a high frequency of opening andclosing.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and variation may be made without departing from what isregarded to be the subject matter of the invention.

What is claimed is:

1. A check valve assembly, comprising:

a. a valve body with a bore defining a flow passage therethrough;

b. a pair of valve flappers pivotally mounted on a shaft within the flowpassage for movement between an open and a closed position;

c. seat means within the valve body against which the flappers can closeto restrict fluid flow through the flow passage; and

d. guide means for securing the shaft to the valve body to facilitatesignificant unrestricted translatory movement of said shaft with respectto said valve body in the direction of the axis of the flow passage,whereby the flappers can open and close without abrasion of theirsurfaces in the area of the shaft.

2. A check valve assembly according to claim 1 wherein the guide meansfor securing the shaft in the valve body comprises a pair of guides, oneat each end of said shaft, retained in elongated open-ended slots thatextend generally parallel to the flow passage axis, said guides beingfreely movable longitudinally in said slots away from and towards theseat means.

3. A check valve assembly according to claim 2 wherein the guides areretained in the slots by adjustable means that facilitate installationand removal of said guides, shaft, and flappers as an assembly into andfrom the valve body.

4. A check valve assembly according to claim 3 wherein each of theguides has a bore for receiving the shaft, means for restricting pivotalmovement of the flappers on said shaft beyond their fully openedposition, and retaining means for releasably engaging the valve body tosecurely but removably retain said guides in said slot.

5. A check valve assembly according to claim 4 wherein the guideretaining means comprises a retaining screw adapted for extendingthrough a longitudinal bore in the guide generally parallel to the flowpassage axis and into releasable engagement with a bore in the valvebody.

6. A check valve assembly according to claim 4 wherein the guideretaining means comprises a resilient split ring adapted for extendingoutwardly from a transverse slot in the guide into an annular groove inthe valve body, said groove having an axial width greater than the axialdimension of said ring,

7. A check valve assembly according to claim 4 wherein the guideretaining means comprises an elongated pin-like element adapted toextend from a bore in the guide into an elongated longitudinal closedslot in the valve body.

8. A check valve assembly according to claim 7 wherein the pin-likeelement comprises a rigid shaft fixed at one end to an opposed end of aresilient shaft-like element.

9. A check valve assembly according to claim 7 wherein the pin-likeelement comprises a helically wound spring.

10. A check valve assembly according to claim 7 wherei I the pin-likeelement comprises a cap-screw adapted for threaded engagement with theguide.

11. A check valve assembly according to claim 7 wherein the pin-likeelement comprises a rigid shaft with an elongated lifting member oflesser cross-sectional dimension extending from one end thereof, andwherein the guide retaining means also includes resilient means forbiasing said pin-like element towards the closed slot when saidretaining means and said guide are installed in the valve body.

12. A chick valve assembly according to claim 7 wherein the pin-likeelement comprises a pipe plug with an elongated nose-like axialextension for engaging the closed slot.

13. A check valve assembly according to claim 12 wherein the axial pipeplug extension terminates in a transverse head for retaining thepin-like element in the guide.

14. A check valve assembly according to claim 1 wherein the seat meansincludes a resilient seat element secured to the valve body incircumscribing relationship to the flow passage.

15. A check valve assembly according to claim 14 wherein the resilientseat element resides in a groove in the seat means surrounding the flowpassage, and wherein the seat element extends significantly out of saidgroove so that it is compressed when the valve flappers are in theirclosed position, and wherein said groove has a greater transversedimension than said seat element to facilitate accommodation ofdisplaced seat element material when said valve flappers are closed.

16. A check valve assembly according to claim 1 wherein the flappers andthe seat means are rigid and non-resilient, and wherein said flappersclose directly against said seat means.

17. A check valve assembly according to claim 1 wherein the valve bodyis devoid of passageways extending from surfaces exposed to internalpressures through its wall toits outside surface.

I t l l 3W3 UNITED STATES PATENT OFFICE (IERTIFICATE OF CORRECTIONPatent No. 3 958 Dated y 25 I 1972 Invent- 3 115) S'atterwhite et al edthat error appears in the above-identified patent I It is certifi ttersPatent are hereby corrected as shown below:

and that said Le Col. 1, line 44, insert valvebefore "body" Col. 4, line16, change "being" to "begin" Col. 6, line 43, enclose "P -in quotationmarks. Col. 8, line 12, change chick to "check" Signed and sealed this24th day of April 1973.

(SEAL) v Attest: I

EDWARD M.FLETCHER,JR. 1 7 ROBERT GOTTSCHALK Attesting Officer 7Commissioner of Patents

1. A check valve assembly, comprising: a. a valve body with a boredefining a flow passage therethrough; b. a pair of valve flapperspivotally mounted on a shaft within the flow passage for movementbetween an open and a closed position; c. seat means within the valvebody against which the flappers can close to restrict fluid flow throughthe flow passage; and d. guide means for securing the shaft to the valvebody to facilitate significant unrestricted translatory movement of saidshaft with respect to said valve body in the direction of the axis ofthe flow passage, whereby the flappers can open and close withoutabrasion of their surfaces in the area of the shaft.
 2. A check valveassembly according to claim 1 wherein the guide means for securing theshaft in the valve body comprises a pair of guides, one at each end ofsaid shaft, retained in elongated open-ended slots that extend generallyparallel to the flow passage axis, said guides being freely movablelongitudinally in said slots away from and towards the seat means.
 3. Acheck valve assembly according to claim 2 wherein the guides areretained in the slots by adjustable meanS that facilitate installationand removal of said guides, shaft, and flappers as an assembly into andfrom the valve body.
 4. A check valve assembly according to claim 3wherein each of the guides has a bore for receiving the shaft, means forrestricting pivotal movement of the flappers on said shaft beyond theirfully opened position, and retaining means for releasably engaging thevalve body to securely but removably retain said guides in said slot. 5.A check valve assembly according to claim 4 wherein the guide retainingmeans comprises a retaining screw adapted for extending through alongitudinal bore in the guide generally parallel to the flow passageaxis and into releasable engagement with a bore in the valve body.
 6. Acheck valve assembly according to claim 4 wherein the guide retainingmeans comprises a resilient split ring adapted for extending outwardlyfrom a transverse slot in the guide into an annular groove in the valvebody, said groove having an axial width greater than the axial dimensionof said ring.
 7. A check valve assembly according to claim 4 wherein theguide retaining means comprises an elongated pin-like element adapted toextend from a bore in the guide into an elongated longitudinal closedslot in the valve body.
 8. A check valve assembly according to claim 7wherein the pin-like element comprises a rigid shaft fixed at one end toan opposed end of a resilient shaft-like element.
 9. A check valveassembly according to claim 7 wherein the pin-like element comprises ahelically wound spring.
 10. A check valve assembly according to claim 7wherein the pin-like element comprises a cap-screw adapted for threadedengagement with the guide.
 11. A check valve assembly according to claim7 wherein the pin-like element comprises a rigid shaft with an elongatedlifting member of lesser cross-sectional dimension extending from oneend thereof, and wherein the guide retaining means also includesresilient means for biasing said pin-like element towards the closedslot when said retaining means and said guide are installed in the valvebody.
 12. A chick valve assembly according to claim 7 wherein thepin-like element comprises a pipe plug with an elongated nose-like axialextension for engaging the closed slot.
 13. A check valve assemblyaccording to claim 12 wherein the axial pipe plug extension terminatesin a transverse head for retaining the pin-like element in the guide.14. A check valve assembly according to claim 1 wherein the seat meansincludes a resilient seat element secured to the valve body incircumscribing relationship to the flow passage.
 15. A check valveassembly according to claim 14 wherein the resilient seat elementresides in a groove in the seat means surrounding the flow passage, andwherein the seat element extends significantly out of said groove sothat it is compressed when the valve flappers are in their closedposition, and wherein said groove has a greater transverse dimensionthan said seat element to facilitate accommodation of displaced seatelement material when said valve flappers are closed.
 16. A check valveassembly according to claim 1 wherein the flappers and the seat meansare rigid and non-resilient, and wherein said flappers close directlyagainst said seat means.
 17. A check valve assembly according to claim 1wherein the valve body is devoid of passageways extending from surfacesexposed to internal pressures through its wall to its outside surface.